So I have a 91 Camaro RS, 5.0 Tbi, rebuilt about 10,000 miles ago.
The motor that is in it is a replacement for a blown motor that was in it originally. Upon putting the new motor in and starting it, we were hearing a loud knocking/clacking noise coming from what 'appeared' to be from the top end of the motor (<-- really hard to tell for sure, though..). I posted a thread earlier trying to diagnose the problem.
Thread containing video of noise

Well, I pulled out the sparkplugs on that side of the motor, and the plug from cyl. 3 has a bent electrode. The electrode is completely bent to one side, and looks a little burned up. It looks as if a piston could be smacking against the electrode, but I am not sure as I am kind of new to this..The other 3 look a little charred, but the electrode is pointing where it needs to be pointing.

Anybody know what could be causing this?

 

What heads, what spark plugs?

Only one thing bends plug electrodes- physical contact. Piston hitting the electrode a TDC or sizable debris getting into the chamber (think: dropping a small screw down the intake) being the most common.

Now, if you have the wrong plugs in the head (long-reach threads vs. short reach) that can obviously cause problems by putting the plug tip way into the chamber and closer to contact with something like the piston or a valve. That's what I'm looking for when I ask about which heads and which plugs you are using.

Also, since spark plugs are not "indexed" in factory heads the electrode can end up pointed in any direction when installed and tightened. Your #3 plug probably won the "I made contact with something first" lottery.

 

Another possiblity is that the electerod was already bent when someone installed it. I'd screw in a new plug, run it and then pull it out and eyeball it.

 

ahhh


so this is the engine with the noise which sounded like rockers needed adjusting. At this point, if it were me, I'd accept that I purchased a pig in a poke which is always the risk when buying someone' junk engine

Personally, I'd yank the engine, tear it down and thoroughly inspect. I have a feeling that you will find that a "recently rebuilt" engine is nothing more than a few parts were tossed at it.

You need to "bite the bullet" and learn exactly what you have.

Yes, it means paying twice for something but that is the risk when buying junkers. People are not always honest or forthcoming.